Function rows_and_track 

pub fn rows_and_track(area: Rect, scrollbar: bool) -> (Rect, Rect)

Splits area into the rows and the scrollbar track beside them, so the track never sits on top of a row. Without a scrollbar the rows get it all.

Every scrolling pane in the UI — list, document, and form — carves its area up this way, and builds its rows to the width this leaves.